Much of our general world knowledge comes in the form of knowledge about the properties and attributes of objects. It is this knowledge that allows us to draw distinctions among objects or events. Sometimes we use this knowledge to make categorical distinctions among objects. For example, we know that elephants are large and fleas are not. Other times, we use this knowledge to make relational judgments about objects. For example, we know that elephants are larger than horses even though both animals are large. The specific aim of this proposal is to provide a coherent account of how context influences our use of this knowledge. In particular, its goal is to determine whether scaling principles developed to explain contextual effects on categorical judgments can be applied relational judgments. The central proposition in this proposal is that context influences an implicit scaling operation in relational judgments in much the same way that it influences the explicit responses of subjects in categorical judgment tasks. A series of experiments will test the validity of this implicit scaling model by comparing performance in relational judgment tasks with the predictions of range-frequency theory. If this approach is successful it should do a great deal to explain how knowledge about the properties of objects is represented and processed. An understanding of these fundamental issues in semantic memory is crucial to a determination of the exact nature of memory impairments in certain forms of dementia. For example, Alzheimer patients appear to have impaired semantic memory function that is absent in the normal old. Currently, it is not known whether these impairments stem primarily from a loss of semantic information, reduced accessibility of this information, or subsequent limitations on its use. A resolution of these latter issues is unlikely in the absence adequate theories of semantic memory.